Adaptive Noise Reduction for Tactical Aircraft Flight Crews

The high ambient noise levels perceived by tactical aircraft flight crews adversely affect their ability to understand desired audio information and warnings, and contribute significantly to overall stress levels. Noise reduction systems are needed that will alleviate the stress-producing ambient noise, and still permit the receipt of desired information. We propose to develop headphones that incorporate active noise reduction using an adaptive feed-forward algorithm. Existing active noise-reducing earphones use nonadaptive feedback techniques. Even the best transducers' performance is ultimatey limited by the group propagation delay around the feedback loop. Feed-forward processes have the potential of predicting the noise pressure at the time the canceling signal emanates from the speaker. The result is a more precise canceling of the unwanted noise, without adverse effects on the quality or strength of the desired signal. We intend to develop the adaptive noise reduction process using circumaural headphones. In Phase II, we propose to transition the technology to insert earphones, which provide better passive isolation. A miniature microphone built into the insert earphone and subjected to the insonified cavity next to the eardrum would enable active noise cancellation.